An uncommon early work by A.A. Cournot (1801-1877), student of Poisson, giant in the history of probability, and father of mathematical economics. "...[Cournot] had the distinction of having been the first to dissociate--in a radical way--various ideas that were still obscure, thus opening the way for deeper and more systematic research by more exact mathematicians. He was also able to show clearly the importance of the applications of the calculus of probability to the scientific description and explanation of human acts (G. Granger in D.S.B.).